


Baby Setters

by Chikita



Category: Haikyuu!!
Genre: Alternate Universe - Brothers, Ambiguous/Open Ending, Anime Spoilers, Child Kageyama Tobio, Child Oikawa Tooru, Family Fluff, Gen, Humor, Kageyama and Oikawa are siblings, Minor Iwaizumi Hajime/Oikawa Tooru, Slice of Life, Tobio is cute but dumb as a brick, Tooru has a puppy crush on Iwa-chan, a bit cracky, minor injury
Language: English
Status: Completed
Published: 2019-10-06
Updated: 2019-10-06
Packaged: 2020-11-26 02:23:52
Rating: General Audiences
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 3,402
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/20922608
Author URL: https://archiveofourown.org/users/Chikita/pseuds/Chikita
Summary: Tooru loves his little brother Tobio, even though he thinks he's secretly an alien. But teaching the little one how to play volleyball might've just been one of his worst ideas. AU, where Oikawa and Kageyama grew up as brothers.





	Baby Setters

**Author's Note:**

> This was originally supposed to be much longer and angstier, but I decided to stay true to myself and make it silly...because that's what I write. The Oikawa & Kageyama are brothers is a kinda popular AU on pixiv. Really, it's an AU that has to exist.
> 
> [German Version](https://www.fanfiktion.de/s/5e6bc3b50004a1be10a67ade/1/Baby-Setters%5BGerman%20Version%5D)

Tobio-chan was an alien.

It was impossible for Tooru to not come to this conclusion. Not after spending almost a decade living under the same roof with his parents and younger brother, who was probably sent by the demon lord to ruin Tooru’s life at some point. They didn’t even _look_ like brothers, maybe adopted siblings or distantly related, swapped at birth cousins of two parallel universes. Okay, maybe that was pushing it a bit. But still, they were as different from each other as two complete strangers.

Tooru came after his mother and grandmother with his chestnut-colored hair, that curled at his ears when it got wet, matching light brown eyes and milky-white skin. Tobio’s hair, on the other hand, fell down straight in silky, black strands, his eyes as big and blue as the open sea.

As a toddler, Tobio was about the cutest thing in the world and not a single day went by where Tooru, despite only being a few years older, wouldn’t attempt to pick him up and carry him across the house. He cooed at him when he slept in his crib, pinched his cheeks whenever he could, and tried to entertain him with silly faces when they ate at the dinner table. Tobio was a quirky child, borderline obsessed with milk, not very talkative, but gifted with, what Tooru called a “resting bitch-face”.

Growing up, not a lot changed about any of those things, except for maybe the crib thing. Tobio wasn’t particularly smart. It took him ages to start talking in complete sentences, use the bathroom instead of a very specific rug in the living room, or eat without smearing food all over his face and clothes.

Their mother used to always scold Tooru for playing too rough with him when they were still small. Maybe Tobio’s scatterbrained nature was a result of his older brother dropping him on his head while roleplaying “space pirates” a few times too often. But even then, he rarely cried unlike most kids when he was upset, and never snitched on him for breaking a house rule.

Tooru loved Tobio. He loved his weird little alien brother, loved how he would sometimes crawl into his futon at night for no particular reason other than to absorb his warmth, and loved how he would follow him around, and stare up to him with those ridiculously huge eyes full of wonder and admiration. His parents were probably surprised by how well they got along, how Tooru, a difficult and fussy child for the most part, showed no sense of jealousy or dislike towards the little bundle of life that was brought into their house one day.

That was until Tooru started picking up a hobby.

\---

Tobio was still in kindergarten when Tooru joined a volleyball club in elementary school. Previously, he’d wanted to do something different, like painting, or making music like his older sister Yuki did, even though she was a teenager back then and rarely even at home. Meeting Hajime, the son of the family who had moved in next door, was the moment, that changed Tooru’s life forever. In good and bad ways.

Hajime soon became “Iwa-chan”, his best friend and later, someone he would consider a soulmate, even if his diary called him something else. Tooru wasn’t sure what it was, that drew him to the scruffy-looking boy who spent most of his free time roaming around outside, climbing and falling off trees, and catching disgusting creatures out in the fields. But the second they met, there was an instant connection.

Joining a club they were both interested in was a natural outcome of their friendship, and an excuse for the two of them to stick to each other even more. At first, Tooru had been reluctant. Sure, he was somewhat athletic and would prefer gym class over math any day. But sadly, he wasn’t one of the kids, who were always picked first whenever they played a soccer match. Every time he did _anything_ in gym class, his teacher would just nod at him with the same satisfied, but unfazed expression.

It was kind of annoying to not be noticed sometimes. Tooru wasn’t the most talented, nor was he the fastest learner when it came to sports. He was painfully average. And sports clubs weren’t made for the “average”. Even as a child, he was smart enough to know that much.

That was until he started actually _playing_ volleyball. Of course, not everything went smooth at first. The ball seemed too big for his small hands, the net silently mocking him whenever one of his serves ended up failing _again,_ and he often came home with his arms covered in blue and red spots. But, after only a few weeks of practice, Tooru started realizing how much he was improving. He’d noticed how his serves stopped hitting the net and enjoyed the feeling of successfully swatting the ball past a row of blockers. Spiking was fun enough, but nothing made his heart swell with pride and some other emotions than Iwa-chan praising him for a toss, that ended in a point for their team.

Tooru had fallen in love. In multiple ways. And it felt like he and Iwa-chan could take on the world if they wanted to.

\---

His parents were disapproving at first, his father rolling his eyes at how Tooru was wasting his time instead of studying math formulas and other boring stuff, and his mother always looking him over with her face twisted in concern. None of his family members paid any attention to Tooru when he was chatting about volleyball at the dinner table, waving his arms through the air to replicate one of Iwa-chan’s spikes he’d set the ball for. No one cared, but his adorable little alien brother Tobio.

As Tooru kept talking and complained loudly whenever his parents were too obvious about their disinterest, his little brother was staring up at him, as if he was the center of the universe. His blue eyes were sparkling bright, curry sauce dripping off his chin as he listened.

“Tobio, your food is getting cold,” their father reminded him with a sigh, but Tobio was too far gone to pay attention, his one-track mind busy figuring out all the things his older brother was raving about. Tobio had grown quite a bit in the past few years, didn’t like to be cuddled and carried around anymore, and had become far too independent for a kid his age, at least in Tooru’s opinion. But maybe, things hadn’t changed all that much. After all, Tobio was still his baby brother.

A strange warmth started pooling in Tooru’s stomach as he went back to eating, and it lasted for a long time after. His parents would never understand his passion. But maybe Tobio would.

“Nii-san, can you teach me volleyball?” Tobio’s small hand tugged at his sleeve, as Tooru was on the way to his room after doing his dishes like the good son he was. He turned around, an amused smile appearing on his face as he looked into the serious, but still freakishly adorable face of his little brother. Tobio’s eyebrows were knitted together in a frown, lip sticking out in a tiny pout, that always reminded Tooru of a fish. For the first time that evening, Tobio had opened his mouth for a purpose other than shoveling food inside.

“You’re too little, Tobio-chan,” Tooru teased him, ruffling his hair and earning an offended huff from the boy, “But I can teach you when you’re older. Who knows, maybe you’ll even be good at it. You kinda suck at most other things.” Tobio puffed up his cheeks at this comment, making Tooru chuckle at how chubby they looked. Okay, maybe he was bullying him a bit too much, but it was the truth. Independent or not, Tobio was five and couldn’t even spell his own name, let alone count to twenty. He would probably have a hard time in school.

\---

When Tooru came home from school one day, Tobio was nowhere to be found. Now, that was unusual. He checked both of their rooms, the kitchen, the living room, even the bathroom, figuring that the little dumbass had fallen asleep on the toilet again. But no. Not this time.

Eventually, Tooru found him standing in the backyard, holding a rubber ball over his head. The look of sheer concentration on Tobio’s face was already funny enough, and when he tossed the ball up into the air and tried to “set” it with his hands, he failed just like anyone his age would. But Tobio wasn’t one to be easily discouraged. Tooru covered his mouth and kept watching Tobio fling the ball up for a couple more minutes, only for it to land on his face _every single time._

At some point, Tooru couldn’t hold back anymore.

“Nii-san, don’t laugh!” Tobio spun around, clutching the ball to his chest as if it was his favorite stuffed animal. The way he said it all angry and flustered only caused Tooru to laugh even harder.

“Are you seriously trying to play volleyball? You don’t even know how to do that,” Tooru couldn’t help but make fun of him. Tobio was so stupid and naive, thinking you could learn a team sport like that all alone, without anyone at least teaching you the basics.

“I saw a match on tv,” Tobio replied, pouting like it was the most obvious answer one could give in that situation. Tooru furrowed his brows. How did Tobio even get their parents to let him watch volleyball on tv? Maybe he’d glared at them with his bitch-face until they finally gave in, or maybe that was the “little brother”-bonus some of his classmates with younger siblings often talked about.

“Look, you have no idea what you’re talking about, Tobio-chan. Volleyball is hard. It takes a lot of practice to be as good as the adults on tv. A _whole lot_ of practice. That’s only something for the big kids, you understand?” Tooru grinned inwardly as Tobio’s eyes widened at his words and wait, was he actually _bowing_ to him?

“I’m a big kid! Please teach me! I wanna be a setter like you! Please, please _please!” _Tooru went silent, crooking his head in confusion. He hadn’t expected Tobio, quiet, grumpy little Tobio to literally beg him for help with a sport he knew next to nothing about. And why a setter? Just because _he_ was one? But even then, even Tooru had wanted to be a spiker at first like most of the other kids, only changing his mind after the coach had advised him to try setting.

Maybe Tobio was a little _too _passionate about this whole volleyball thing. But even then, Tooru couldn’t deny that being idolized like that made him feel strangely proud. It wasn’t like teaching Tobio how to play around a little would do any harm, right? _Right._

“Well, I hope you know how lucky you are,” Tooru said with a smirk, relishing in the fact that Tobio was completely dependent on him for once. Tobio nodded fiercely, eyes shining with gratitude, and held his arms out to give him the ball. It was already stained with dirt and mud, and Tooru hesitated a few seconds before accepting it with a grimace. He very much preferred playing volleyball in a gym, but given Tobio’s equally dirt-stained face and hands, the little one didn’t seem to care either way.

Tooru decided to start with something easy. Throwing the ball to each other and catching it with both hands every time was good practice for volleyball beginners. This was how Tooru had been taught at school after all. Ball control was an essential part of the sport and without it, you were pretty much doomed from the start.

Tobio did everything Tooru told him to, never fussed or complained, but after only a few minutes of practice, his trademark frown started deepening. From the way he was fidgeting on the spot, Tooru guessed he either really had to pee or was simply getting bored of their little game. If the former was the case, Tooru would notice it soon enough.

“You're not half-bad, Tobio-chan. For a noob at least,” Tooru said after a while and melted when Tobio actually started _blushing_ at his words. As if the little guy couldn't possibly get more adorable. “Let's try something more difficult. You wanna learn volleyball like the players on tv, right?” Tobio nodded so hard that Tooru feared he was about to give himself a concussion.

And so Tooru showed him. He showed him how to position his hands when tossing the ball, how to do underhand receives, and last but not least, how to serve. The last part was Tooru's favorite because he got to show off a little and laugh at Tobio when his own attempts at an overhand serve led him to slam the ball right into a mud puddle and splash even more dirty water up in his face.

"You sure suck at serving," Tooru said every time it happened, remembering how the coach would always call his serve "beautiful, but powerful". Now he got to see what an "ugly and weak" serve looked like, but he wasn't going to be rude about it. His own serves hadn't been all that good when he'd started out either. It was okay for Tobio to suck. Hell, he was _supposed_ to suck. Everything else would just be creepy.

They kept playing like this for a while. It wasn't long until Tooru's arms and legs started getting heavy. School and the long walk home had taken its toll on him, and even though he could spend hours practicing with Iwa-chan, something about doing it with Tobio-chan was different. Maybe it was due to him trying harder to impress his baby brother. Or maybe it was because it seemed natural for siblings to have some sort of rivalry going on, even if the younger one was an inexperienced, clumsy little dork with curry buns for brain cells.

If there was one quality Tobio possessed, it had to be stamina. He always asked for more sets to be thrown his way and didn’t mind running after stray balls whenever he couldn’t get his hands on them in the air. Even though they didn’t use a real volleyball, Tooru didn’t miss the way Tobio's arms would sometimes flinch away from the ball out of reflex when they practiced receives. His face twisted in what had to be pain, but that wasn’t enough for him to stop. Quite the opposite, he still asked for more. More and more and more...

"Alright, you little tyrant, this is the last one for today," Tooru decided as he threw the ball again, slightly irritated by Tobio's excessive demands. It was getting dark outside, and he still didn’t look tired. Maybe he really _was_ an alien after all. Tobio raised his arms up high into the air, his eyes following the ball like a cat would do with a laser pointer. Tooru waited for the moment where he would either miss or touch the ball with his fingertips and _maybe_ get it to move a few inches forward at most before falling onto his butt.

Sadly, that moment never arrived, nor did the familiar noise of unskilled, grubby little hands making contact with the round object. Before Tooru realized what was happening, the ball went up without so much as a sound, floating through the air in a perfect arch. Tooru’s jaw dropped, as he was stunned into silence.

_What the hell? _

Before he could even think of moving his hands up to send the toss back to Tobio, the ball was suddenly too close to his own face. _Far too_ close. His short life of seven and a half years was flashing before his eyes. Now he would _never_ get married to Iwa-chan after all.

A dull _thud _echoed through the air. At this point, Tooru had to sympathize with Tobio, for doing the same thing to himself multiple times in a row, the ball bouncing off his face, hitting the ground and rolling out of sight.

“Ouch!”, Tooru cried out more out of shock and outrage, than actual pain, and moved a hand up to his nose, that started dripping with something warm. He was prone to nosebleeds, so getting one now wasn’t all that scary, just extremely unpleasant. When he looked back up, Tobio stared at him with that confused puppy look he always used on everyone. Tooru expected an apology, but what came out of Tobio’s mouth instead completely floored him.

“Was that a good toss?”

\---

Half an hour later, Tooru still wasn’t sure why Tobio’s “innocent” question made him want to rip his head off and cry at the same time. Lucky enough, their mother had intervened before even more bodily fluids could be spilled, and scolded them for looking like “little pigs”, especially Tooru, since he hadn’t even bothered changing out of his school uniform after coming home. Before they knew it, they were pulled inside and dropped off in the bathroom. The two of them were supposed to take a bath that evening anyway, so it didn’t really make a difference. Even though staying clean through all of dinner would prove to be a challenge, at least for Tobio.

Tooru sat at the far end of the bathtub, leaning over the rim with his arms crossed and his mouth twisted into a pout. The water was a little too hot to his liking, but that wasn’t what he was the most annoyed about. A few feet across, a naked Tobio was sitting on a stool with mom crouching behind him to scrub the dirt out of his hair and off his face. The whole atmosphere had something relaxing and peaceful, and yet, Tooru was brooding.

That toss back then couldn’t have been anything but a fluke. Tobio was in _kindergarten. _Independent or not, he was very much a small child. A child, who took naps during the day, slept with his blankie and stuffed animals, and _still_ liked to drink his milk out of a sippy cup whenever mom and dad weren’t watching. Okay, the last one was weird, even for Tobio’s age.

But still, Tobio couldn’t be better at tossing than he was. Not after only watching a match on tv and playing outside for a few hours, when Tooru was working his butt off at the school’s volleyball club to get a few balls over the net. It was weird and honestly, frustrating.

What if Tobio kept playing volleyball and joined Tooru’s team in middle school, snatching his role as the main setter because he was more talented? That would be pretty bad. Or worse, what if he went to a former powerhouse high school, met an orange-haired gremlin child who could move fast and jump very high, and crushed Tooru’s team in the semi-finals of a tournament, forcing them to give up their dreams of ever going to nationals.

That was a little specific. But_ what if?_

“Did you two have a fight?”, his mother asked after neither of the boys had said a word to each other, not even after she had dropped little Tobio into the tub next to Tooru.

“No,” Tooru replied but averted his eyes when Tobio first looked at him, then started poking his cheek with his finger. Tooru fought the urge to dip him underwater. Their mother raised her eyebrows at the two boys, but Tooru only shrugged. The nosebleed probably looked a bit suspicious.

“Look, I don’t know what happened out there, but you should talk about it, at least with each other. You won’t make it better by sulking.” their mom said, but the only one listening was Tooru. Tobio, on the other hand, had gone from bothering Tooru, to holding his toy boat over his head, and tossing it up a few times as if it was a volleyball. His eyes were wide and focused, tongue sticking out in concentration. Tooru watched him do it over and over, a shiver crawling up his spine despite the hot water.

“Oh no,” Tooru whispered to himself as the realization dawned upon him, “I think, I’ve just created a monster.”

**Author's Note:**

> I probably made Tooru a bit too smart in this, given that I have a kindergarten AU in german where he's 5 and acts below his age, but ehh...


End file.
